The present invention relates to light distribution features for light fixtures, and particularly, to providing a light fixture with a compact spot reflector system for small area light sources such as LEDs and LDs.
Traditional light sources for outdoor, industrial, office, or household lighting include incandescent, fluorescent, and high-intensity discharge (HID) lamps. Some of these traditional light sources provide a point or a linear lighting element; however, the glass enclosure around the element required that reflectors be displaced from the element. Therefore, with traditional light sources, reflectors often were required to extend around the light source in all three axes.
Newer highly efficient lighting technology, such as diode light sources, including LEDs or laser diodes (LDs), are generally arranged in a small area planar array, referred to as a light emitter or package. Such a light emitter may include a single chip containing one or more diode light sources, or may contain multiple chips.
A diode-type light emitter provides the added advantage that all of the light is directed outward from the planar array so that no reflector is required behind the array. In cases where the light emitter package contains one or more diodes on a single chip, the source of light is very, very small, so using a total internal reflection lens (TIR lens) is often practical. A TIR lens includes facets on the entry face (diode/chip side) of the lens that are positioned and angled to redirect all the light incident from the entry face toward the exit face; however, TIR lenses have shortcomings when designed for multi-chip light emitters; therefore, even though the source of light is still closer to a point source than for traditional lighting sources, traditional reflectors are often used to redirect the light as desired in light emitters using multiple chips.
One common requirement for redirecting traditional lighting or light emitter sources is providing a spot distribution pattern. One prior art solution used for limiting the distribution in traditional lighting is a curved conical frustum reflector, for example, with a parabolic profile, providing redirection of light; however, the smaller the desired spot at a given range from the light fixture, the longer the length the reflector must extend from the light source in order to obtain the desired beam distribution and minimize spill light. Another prior art reflector system for traditional lighting provides a pair of concentric reflectors having cylindrical profiles, each with a different diameter. Such a reflector system does shape the light beam to a spot; however, such a system can be inefficient if less expensive reflectors are used, because a given light ray is reflected multiple times before escaping out the distal end of the reflector.
Another prior art reflector system for traditional lighting provides nested concentric reflectors; however, such reflector systems are not designed for a point or near point light source as is provided by modern diode-type light emitters, but rather are designed for a linear or area light source. Such a reflector system designed for area light sources combined with a diode-type light emitter does not efficiently or effectively redirect light to a desired spot pattern and would therefore require a higher output light emitter than preferred in order to provide the desired lumens for the desired spot distribution pattern, thus undermining the energy efficiency that is possible with diode-type light emitters.
Therefore, it is desirable to provide a light fixture reflector system that is structured to provide the redirection necessary from a very small, point or near point light source, sustaining the efficiency advantages available with diode-type light emitter package, while also providing the desired spot distribution pattern and minimizing spill light.